The present invention relates to an assembly comprising a supporting tubular body and an elastically expanded sleeve fitted thereon and in particular, to sleeves of such type for electric cable joints and sealing ends.
Although the invention will be described in connection with covering sleeves for electric cable joints and to the associated supporting tubular bodies, it is to be understood that the covering sleeves of the invention can be applied to any whatsoever cylindrical body, such as, for example, tubes, bars, stems and the like, on which an elastically expanded and collapsible covering sleeve is to be applied, for example, for the local protection from the corrosion. Moreover, although the description of the present invention makes a detailed reference to the electric cable joints, it is to be understood that the invention can be applied similarly on the ends of the cables themselves, and moreover, can also be applied at any point on any cylindrical body, independently of the presence of joints or discontinuities in its structure.
In order to provide joints between electric cables, the conductors of the cables to be interconnected are locally stripped of the insulation surrounding them, and the space corresponding to the removed insulation is then filled with suitable means. Thereafter, a sleeve of one or more layers is disposed around the connecting zone.
Said sleeve, the characteristics of which are well known in the art, must be fitted on one of the cables, before their connection, and then slid on the joined cables until it is in the correct position on the joint. Subsequently, the sleeve must be able to tightly engage the surfaces of the cable insulations.
To this end, the sleeve is supported in radially and elastically expanded condition by a sufficiently rigid tubular element which has an inner diameter greater than the outer diameter of the cables and which can slide freely on them. At the desired time, the tubular supporting element can be then removed so that the sleeve contracts elastically and tightens on the cables as desired.
The radially inward pressure corresponding to the radial expansion of the sleeve is considerable since the sleeves can be expanded up to 200-300%. In particular, if it is desired to use a single sleeve for more than one cable outer diameter, the sleeve itself must be subject to a particularly greater expansion than would be necessary if the sleeve were designed for only one cable diameter.
Sleeves of this type are, for example, described in U.S. application Ser. No. 07/464,370 filed Jan. 12, 1990 of the assignee of the present application.
There are known tubular elements for supporting sleeves which can be removed, allowing the sleeve contraction, by means of an axial unthreading as described in the European Patent No. 149 032 of the assignee of the present application. Said tubular elements easily withstand the pressure applied thereto by the sleeve, but they must be unthreaded by means of suitable tools because of the high friction between the outer surface of the supporting element and the inner surface of the sleeve. Accordingly, their use is laborious.
Supporting tubular elements are also known from the English Patent No. 1 292 608, and such elements are formed by a tape, or the like, wound as a helix having contiguous turns. Said tubular element can be removed by unwinding the helix through a pulling action exerted on one end of the tape which has been previously unwound at one extremity of the tubular body, introduced into it and pulled at the opposite extremity. In said manner, the tubular element so formed is eliminated with the least effort from the inside of the sleeve and the relative operations can be carried out manually without particular tools.
However, the known wound structure is suitable only for supporting sleeves of small thickness or not greatly expanded since the known wound tapes must have a relatively small thickness which means that the tubular bodies have a thin wall, i.e. not sufficient to bear the inward pressure imposed by the greatly expanded sleeves previously described.
In fact, the use in the known wound structure of tapes having a greater thickness, corresponding to the required resistance, is not possible because said tapes would be to rigid for being bent sufficiently to be introduced into the base of the tubular supporting element, in the space available for them between cables and the tubular element itself, in order to provide the unwinding described above.
The main object of the present invention is to provide an assembly of the above-indicated type comprising a sleeve on a supporting tubular body which is formed by a tape wound as a helix and which is sufficiently flexible to be removed by means of an easy manual pulling action at one end of the tape but which has, at the same time, a structure having a size with the thicknesses necessary to bear the stresses caused by its use with sleeves of large thickness and subjected to substantial radial expansions and thereby exerting corresponding forces of elastic contraction.